multi.c

/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2011, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at http://curl.haxx.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ***************************************************************************/

#include "setup.h"

#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include <curl/curl.h>

#include "urldata.h"
#include "transfer.h"
#include "url.h"
#include "connect.h"
#include "progress.h"
#include "easyif.h"
#include "multiif.h"
#include "sendf.h"
#include "timeval.h"
#include "http.h"
#include "warnless.h"

#define _MPRINTF_REPLACE /* use our functions only */
#include <curl/mprintf.h>

#include "curl_memory.h"
/* The last #include file should be: */
#include "memdebug.h"

/*
  CURL_SOCKET_HASH_TABLE_SIZE should be a prime number. Increasing it from 97
  to 911 takes on a 32-bit machine 4 x 804 = 3211 more bytes.  Still, every
  CURL handle takes 45-50 K memory, therefore this 3K are not significant.
*/
#ifndef CURL_SOCKET_HASH_TABLE_SIZE
#define CURL_SOCKET_HASH_TABLE_SIZE 911
#endif

struct Curl_message {
  /* the 'CURLMsg' is the part that is visible to the external user */
  struct CURLMsg extmsg;
};

/* NOTE: if you add a state here, add the name to the statename[] array as
   well!
*/
typedef enum {
  CURLM_STATE_INIT,        /* 0 - start in this state */
  CURLM_STATE_CONNECT,     /* 1 - resolve/connect has been sent off */
  CURLM_STATE_WAITRESOLVE, /* 2 - awaiting the resolve to finalize */
  CURLM_STATE_WAITCONNECT, /* 3 - awaiting the connect to finalize */
  CURLM_STATE_WAITPROXYCONNECT, /* 4 - awaiting proxy CONNECT to finalize */
  CURLM_STATE_PROTOCONNECT, /* 5 - completing the protocol-specific connect
                               phase */
  CURLM_STATE_WAITDO,      /* 6 - wait for our turn to send the request */
  CURLM_STATE_DO,          /* 7 - start send off the request (part 1) */
  CURLM_STATE_DOING,       /* 8 - sending off the request (part 1) */
  CURLM_STATE_DO_MORE,     /* 9 - send off the request (part 2) */
  CURLM_STATE_DO_DONE,     /* 10 - done sending off request */
  CURLM_STATE_WAITPERFORM, /* 11 - wait for our turn to read the response */
  CURLM_STATE_PERFORM,     /* 12 - transfer data */
  CURLM_STATE_TOOFAST,     /* 13 - wait because limit-rate exceeded */
  CURLM_STATE_DONE,        /* 14 - post data transfer operation */
  CURLM_STATE_COMPLETED,   /* 15 - operation complete */
  CURLM_STATE_MSGSENT,     /* 16 - the operation complete message is sent */
  CURLM_STATE_LAST         /* 17 - not a true state, never use this */
} CURLMstate;

/* we support N sockets per easy handle. Set the corresponding bit to what
   action we should wait for */
#define MAX_SOCKSPEREASYHANDLE 5
#define GETSOCK_READABLE (0x00ff)
#define GETSOCK_WRITABLE (0xff00)

struct closure {
  struct closure *next; /* a simple one-way list of structs */
  struct SessionHandle *easy_handle;
};

struct Curl_one_easy {
  /* first, two fields for the linked list of these */
  struct Curl_one_easy *next;
  struct Curl_one_easy *prev;

  struct SessionHandle *easy_handle; /* the easy handle for this unit */
  struct connectdata *easy_conn;     /* the "unit's" connection */

  CURLMstate state;  /* the handle's state */
  CURLcode result;   /* previous result */

  struct Curl_message msg; /* A single posted message. */

  /* Array with the plain socket numbers this handle takes care of, in no
     particular order. Note that all sockets are added to the sockhash, where
     the state etc are also kept. This array is mostly used to detect when a
     socket is to be removed from the hash. See singlesocket(). */
  curl_socket_t sockets[MAX_SOCKSPEREASYHANDLE];
  int numsocks;
};

#define CURL_MULTI_HANDLE 0x000bab1e

#define GOOD_MULTI_HANDLE(x) \
  ((x)&&(((struct Curl_multi *)(x))->type == CURL_MULTI_HANDLE))
#define GOOD_EASY_HANDLE(x) \
 (((struct SessionHandle *)(x))->magic == CURLEASY_MAGIC_NUMBER)

/* This is the struct known as CURLM on the outside */
struct Curl_multi {
  /* First a simple identifier to easier detect if a user mix up
     this multi handle with an easy handle. Set this to CURL_MULTI_HANDLE. */
  long type;

  /* We have a linked list with easy handles */
  struct Curl_one_easy easy;

  int num_easy; /* amount of entries in the linked list above. */
  int num_alive; /* amount of easy handles that are added but have not yet
                    reached COMPLETE state */

  struct curl_llist *msglist; /* a list of messages from completed transfers */

  /* callback function and user data pointer for the *socket() API */
  curl_socket_callback socket_cb;
  void *socket_userp;

  /* Hostname cache */
  struct curl_hash *hostcache;

  /* timetree points to the splay-tree of time nodes to figure out expire
     times of all currently set timers */
  struct Curl_tree *timetree;

  /* 'sockhash' is the lookup hash for socket descriptor => easy handles (note
     the pluralis form, there can be more than one easy handle waiting on the
     same actual socket) */
  struct curl_hash *sockhash;

  /* Whether pipelining is enabled for this multi handle */
  bool pipelining_enabled;

  /* shared connection cache */
  struct conncache *connc;
  long maxconnects; /* if >0, a fixed limit of the maximum number of entries
                       we're allowed to grow the connection cache to */

  /* list of easy handles kept around for doing nice connection closures */
  struct closure *closure;

  /* timer callback and user data pointer for the *socket() API */
  curl_multi_timer_callback timer_cb;
  void *timer_userp;
  struct timeval timer_lastcall; /* the fixed time for the timeout for the
                                    previous callback */
};

static void multi_connc_remove_handle(struct Curl_multi *multi,
                                      struct SessionHandle *data);
static void singlesocket(struct Curl_multi *multi,
                         struct Curl_one_easy *easy);
static CURLMcode add_closure(struct Curl_multi *multi,
                             struct SessionHandle *data);
static int update_timer(struct Curl_multi *multi);

static CURLcode addHandleToSendOrPendPipeline(struct SessionHandle *handle,
                                              struct connectdata *conn);
static int checkPendPipeline(struct connectdata *conn);
static void moveHandleFromSendToRecvPipeline(struct SessionHandle *handle,
                                             struct connectdata *conn);
static void moveHandleFromRecvToDonePipeline(struct SessionHandle *handle,
                                             struct connectdata *conn);
static bool isHandleAtHead(struct SessionHandle *handle,
                           struct curl_llist *pipeline);
static CURLMcode add_next_timeout(struct timeval now,
                                  struct Curl_multi *multi,
                                  struct SessionHandle *d);

#ifdef DEBUGBUILD
static const char * const statename[]={
  "INIT",
  "CONNECT",
  "WAITRESOLVE",
  "WAITCONNECT",
  "WAITPROXYCONNECT",
  "PROTOCONNECT",
  "WAITDO",
  "DO",
  "DOING",
  "DO_MORE",
  "DO_DONE",
  "WAITPERFORM",
  "PERFORM",
  "TOOFAST",
  "DONE",
  "COMPLETED",
  "MSGSENT",
};
#endif

static void multi_freetimeout(void *a, void *b);

/* always use this function to change state, to make debugging easier */
static void multistate(struct Curl_one_easy *easy, CURLMstate state)
{
#ifdef DEBUGBUILD
  long connectindex = -5000;
#endif
  CURLMstate oldstate = easy->state;

  if(oldstate == state)
    /* don't bother when the new state is the same as the old state */
    return;

  easy->state = state;

#ifdef DEBUGBUILD
  if(easy->easy_conn) {
    if(easy->state > CURLM_STATE_CONNECT &&
       easy->state < CURLM_STATE_COMPLETED)
      connectindex = easy->easy_conn->connectindex;

    infof(easy->easy_handle,
          "STATE: %s => %s handle %p; (connection #%ld) \n",
          statename[oldstate], statename[easy->state],
          (char *)easy, connectindex);
  }
#endif
  if(state == CURLM_STATE_COMPLETED)
    /* changing to COMPLETED means there's one less easy handle 'alive' */
    easy->easy_handle->multi->num_alive--;
}

/*
 * We add one of these structs to the sockhash for a particular socket
 */

struct Curl_sh_entry {
  struct SessionHandle *easy;
  time_t timestamp;
  int action;  /* what action READ/WRITE this socket waits for */
  curl_socket_t socket; /* mainly to ease debugging */
  void *socketp; /* settable by users with curl_multi_assign() */
};
/* bits for 'action' having no bits means this socket is not expecting any
   action */
#define SH_READ  1
#define SH_WRITE 2

/* make sure this socket is present in the hash for this handle */
static struct Curl_sh_entry *sh_addentry(struct curl_hash *sh,
                                         curl_socket_t s,
                                         struct SessionHandle *data)
{
  struct Curl_sh_entry *there =
    Curl_hash_pick(sh, (char *)&s, sizeof(curl_socket_t));
  struct Curl_sh_entry *check;

  if(there)
    /* it is present, return fine */
    return there;

  /* not present, add it */
  check = calloc(1, sizeof(struct Curl_sh_entry));
  if(!check)
    return NULL; /* major failure */
  check->easy = data;
  check->socket = s;

  /* make/add new hash entry */
  if(NULL == Curl_hash_add(sh, (char *)&s, sizeof(curl_socket_t), check)) {
    free(check);
    return NULL; /* major failure */
  }

  return check; /* things are good in sockhash land */
}


/* delete the given socket + handle from the hash */
static void sh_delentry(struct curl_hash *sh, curl_socket_t s)
{
  struct Curl_sh_entry *there =
    Curl_hash_pick(sh, (char *)&s, sizeof(curl_socket_t));

  if(there) {
    /* this socket is in the hash */
    /* We remove the hash entry. (This'll end up in a call to
       sh_freeentry().) */
    Curl_hash_delete(sh, (char *)&s, sizeof(curl_socket_t));
  }
}

/*
 * free a sockhash entry
 */
static void sh_freeentry(void *freethis)
{
  struct Curl_sh_entry *p = (struct Curl_sh_entry *) freethis;

  if(p)
    free(p);
}

static size_t fd_key_compare(void*k1, size_t k1_len, void*k2, size_t k2_len)
{
  (void) k1_len; (void) k2_len;

  return (*((int* ) k1)) == (*((int* ) k2));
}

static size_t hash_fd(void* key, size_t key_length, size_t slots_num)
{
  int fd = * ((int* ) key);
  (void) key_length;

  return (fd % (int)slots_num);
}

/*
 * sh_init() creates a new socket hash and returns the handle for it.
 *
 * Quote from README.multi_socket:
 *
 * "Some tests at 7000 and 9000 connections showed that the socket hash lookup
 * is somewhat of a bottle neck. Its current implementation may be a bit too
 * limiting. It simply has a fixed-size array, and on each entry in the array
 * it has a linked list with entries. So the hash only checks which list to
 * scan through. The code I had used so for used a list with merely 7 slots
 * (as that is what the DNS hash uses) but with 7000 connections that would
 * make an average of 1000 nodes in each list to run through. I upped that to
 * 97 slots (I believe a prime is suitable) and noticed a significant speed
 * increase.  I need to reconsider the hash implementation or use a rather
 * large default value like this. At 9000 connections I was still below 10us
 * per call."
 *
 */
static struct curl_hash *sh_init(void)
{
  return Curl_hash_alloc(CURL_SOCKET_HASH_TABLE_SIZE, hash_fd, fd_key_compare,
                         sh_freeentry);
}

/*
 * multi_addmsg()
 *
 * Called when a transfer is completed. Adds the given msg pointer to
 * the list kept in the multi handle.
 */
static CURLMcode multi_addmsg(struct Curl_multi *multi,
                              struct Curl_message *msg)
{
  if(!Curl_llist_insert_next(multi->msglist, multi->msglist->tail, msg))
    return CURLM_OUT_OF_MEMORY;

  return CURLM_OK;
}

/*
 * multi_freeamsg()
 *
 * Callback used by the llist system when a single list entry is destroyed.
 */
static void multi_freeamsg(void *a, void *b)
{
  (void)a;
  (void)b;
}


CURLM *curl_multi_init(void)
{
  struct Curl_multi *multi = calloc(1, sizeof(struct Curl_multi));

  if(!multi)
    return NULL;

  multi->type = CURL_MULTI_HANDLE;

  multi->hostcache = Curl_mk_dnscache();
  if(!multi->hostcache)
    goto error;

  multi->sockhash = sh_init();
  if(!multi->sockhash)
    goto error;

  multi->connc = Curl_mk_connc(CONNCACHE_MULTI, -1L);
  if(!multi->connc)
    goto error;

  multi->msglist = Curl_llist_alloc(multi_freeamsg);
  if(!multi->msglist)
    goto error;

  /* Let's make the doubly-linked list a circular list.  This makes
     the linked list code simpler and allows inserting at the end
     with less work (we didn't keep a tail pointer before). */
  multi->easy.next = &multi->easy;
  multi->easy.prev = &multi->easy;

  return (CURLM *) multi;

  error:
  if(multi->sockhash)
    Curl_hash_destroy(multi->sockhash);
  if(multi->hostcache)
    Curl_hash_destroy(multi->hostcache);
  if(multi->connc)
    Curl_rm_connc(multi->connc);

  free(multi);
  return NULL;
}

CURLMcode curl_multi_add_handle(CURLM *multi_handle,
                                CURL *easy_handle)
{
  struct Curl_multi *multi=(struct Curl_multi *)multi_handle;
  struct Curl_one_easy *easy;
  struct closure *cl;
  struct closure *prev=NULL;
  struct SessionHandle *data = easy_handle;

  /* First, make some basic checks that the CURLM handle is a good handle */
  if(!GOOD_MULTI_HANDLE(multi))
    return CURLM_BAD_HANDLE;

  /* Verify that we got a somewhat good easy handle too */
  if(!GOOD_EASY_HANDLE(easy_handle))
    return CURLM_BAD_EASY_HANDLE;

  /* Prevent users to add the same handle more than once! */
  if(((struct SessionHandle *)easy_handle)->multi)
    /* possibly we should create a new unique error code for this condition */
    return CURLM_BAD_EASY_HANDLE;

  data->state.timeoutlist = Curl_llist_alloc(multi_freetimeout);
  if(!data->state.timeoutlist)
    return CURLM_OUT_OF_MEMORY;

  /* Now, time to add an easy handle to the multi stack */
  easy = calloc(1, sizeof(struct Curl_one_easy));
  if(!easy)
    return CURLM_OUT_OF_MEMORY;

  cl = multi->closure;
  while(cl) {
    struct closure *next = cl->next;
    if(cl->easy_handle == (struct SessionHandle *)easy_handle) {
      /* remove this handle from the closure list */
      free(cl);
      if(prev)
        prev->next = next;
      else
        multi->closure = next;
      break; /* no need to continue since this handle can only be present once
                in the list */
    }
    prev = cl;
    cl = next;
  }

  /* set the easy handle */
  easy->easy_handle = easy_handle;
  multistate(easy, CURLM_STATE_INIT);

  /* set the back pointer to one_easy to assist in removal */
  easy->easy_handle->multi_pos =  easy;

  /* for multi interface connections, we share DNS cache automatically if the
     easy handle's one is currently private. */
  if(easy->easy_handle->dns.hostcache &&
     (easy->easy_handle->dns.hostcachetype == HCACHE_PRIVATE)) {
    Curl_hash_destroy(easy->easy_handle->dns.hostcache);
    easy->easy_handle->dns.hostcache = NULL;
    easy->easy_handle->dns.hostcachetype = HCACHE_NONE;
  }

  if(!easy->easy_handle->dns.hostcache ||
     (easy->easy_handle->dns.hostcachetype == HCACHE_NONE)) {
    easy->easy_handle->dns.hostcache = multi->hostcache;
    easy->easy_handle->dns.hostcachetype = HCACHE_MULTI;
  }

  if(easy->easy_handle->state.connc) {
    if(easy->easy_handle->state.connc->type == CONNCACHE_PRIVATE) {
      /* kill old private version */
      Curl_rm_connc(easy->easy_handle->state.connc);
      /* point out our shared one instead */
      easy->easy_handle->state.connc = multi->connc;
    }
    /* else it is already using multi? */
  }
  else
    /* point out our shared one */
    easy->easy_handle->state.connc = multi->connc;

  /* Make sure the type is setup correctly */
  easy->easy_handle->state.connc->type = CONNCACHE_MULTI;

  /* This adds the new entry at the back of the list
     to try and maintain a FIFO queue so the pipelined
     requests are in order. */

  /* We add this new entry last in the list. We make our 'next' point to the
     'first' struct and our 'prev' point to the previous 'prev' */
  easy->next = &multi->easy;
  easy->prev = multi->easy.prev;

  /* make 'easy' the last node in the chain */
  multi->easy.prev = easy;

  /* if there was a prev node, make sure its 'next' pointer links to
     the new node */
  easy->prev->next = easy;

  Curl_easy_addmulti(easy_handle, multi_handle);

  /* make the SessionHandle struct refer back to this struct */
  easy->easy_handle->set.one_easy = easy;

  /* Set the timeout for this handle to expire really soon so that it will
     be taken care of even when this handle is added in the midst of operation
     when only the curl_multi_socket() API is used. During that flow, only
     sockets that time-out or have actions will be dealt with. Since this
     handle has no action yet, we make sure it times out to get things to
     happen. */
  Curl_expire(easy->easy_handle, 1);

  /* increase the node-counter */
  multi->num_easy++;

  if((multi->num_easy * 4) > multi->connc->num) {
    /* We want the connection cache to have plenty room. Before we supported
       the shared cache every single easy handle had 5 entries in their cache
       by default. */
    long newmax = multi->num_easy * 4;

    if(multi->maxconnects && (multi->maxconnects < newmax))
      /* don't grow beyond the allowed size */
      newmax = multi->maxconnects;

    if(newmax > multi->connc->num) {
      /* we only do this is we can in fact grow the cache */
      CURLcode res = Curl_ch_connc(easy_handle, multi->connc, newmax);
      if(res != CURLE_OK) {
        /* FIXME: may need to do more cleanup here */
        curl_multi_remove_handle(multi_handle, easy_handle);
        return CURLM_OUT_OF_MEMORY;
      }
    }
  }

  /* increase the alive-counter */
  multi->num_alive++;

  /* A somewhat crude work-around for a little glitch in update_timer() that
     happens if the lastcall time is set to the same time when the handle is
     removed as when the next handle is added, as then the check in
     update_timer() that prevents calling the application multiple times with
     the same timer infor will not trigger and then the new handle's timeout
     will not be notified to the app.

     The work-around is thus simply to clear the 'lastcall' variable to force
     update_timer() to always trigger a callback to the app when a new easy
     handle is added */
  memset(&multi->timer_lastcall, 0, sizeof(multi->timer_lastcall));

  update_timer(multi);
  return CURLM_OK;
}

#if 0
/* Debug-function, used like this:
 *
 * Curl_hash_print(multi->sockhash, debug_print_sock_hash);
 *
 * Enable the hash print function first by editing hash.c
 */
static void debug_print_sock_hash(void *p)
{
  struct Curl_sh_entry *sh = (struct Curl_sh_entry *)p;

  fprintf(stderr, " [easy %p/magic %x/socket %d]",
          (void *)sh->easy, sh->easy->magic, (int)sh->socket);
}
#endif

CURLMcode curl_multi_remove_handle(CURLM *multi_handle,
                                   CURL *curl_handle)
{
  struct Curl_multi *multi=(struct Curl_multi *)multi_handle;
  struct Curl_one_easy *easy;
  struct SessionHandle *data = curl_handle;

  /* First, make some basic checks that the CURLM handle is a good handle */
  if(!GOOD_MULTI_HANDLE(multi))
    return CURLM_BAD_HANDLE;

  /* Verify that we got a somewhat good easy handle too */
  if(!GOOD_EASY_HANDLE(curl_handle))
    return CURLM_BAD_EASY_HANDLE;

  /* pick-up from the 'curl_handle' the kept position in the list */
  easy = data->multi_pos;

  if(easy) {
    bool premature = (easy->state < CURLM_STATE_COMPLETED) ? TRUE : FALSE;
    bool easy_owns_conn = (easy->easy_conn &&
                           (easy->easy_conn->data == easy->easy_handle)) ?
                           TRUE : FALSE;

    /* If the 'state' is not INIT or COMPLETED, we might need to do something
       nice to put the easy_handle in a good known state when this returns. */
    if(premature)
      /* this handle is "alive" so we need to count down the total number of
         alive connections when this is removed */
      multi->num_alive--;

    if(easy->easy_conn &&
       (easy->easy_conn->send_pipe->size +
        easy->easy_conn->recv_pipe->size > 1) &&
       easy->state > CURLM_STATE_WAITDO &&
       easy->state < CURLM_STATE_COMPLETED) {
      /* If the handle is in a pipeline and has started sending off its
         request but not received its response yet, we need to close
         connection. */
      easy->easy_conn->bits.close = TRUE;
      /* Set connection owner so that Curl_done() closes it.
         We can sefely do this here since connection is killed. */
      easy->easy_conn->data = easy->easy_handle;
    }

    /* The timer must be shut down before easy->multi is set to NULL,
       else the timenode will remain in the splay tree after
       curl_easy_cleanup is called. */
    Curl_expire(easy->easy_handle, 0);

    /* destroy the timeout list that is held in the easy handle */
    if(data->state.timeoutlist) {
      Curl_llist_destroy(data->state.timeoutlist, NULL);
      data->state.timeoutlist = NULL;
    }

    if(easy->easy_handle->dns.hostcachetype == HCACHE_MULTI) {
      /* clear out the usage of the shared DNS cache */
      easy->easy_handle->dns.hostcache = NULL;
      easy->easy_handle->dns.hostcachetype = HCACHE_NONE;
    }

    if(easy->easy_conn) {

      /* we must call Curl_done() here (if we still "own it") so that we don't
         leave a half-baked one around */
      if(easy_owns_conn) {

        /* Curl_done() clears the conn->data field to lose the association
           between the easy handle and the connection

           Note that this ignores the return code simply because there's
           nothing really useful to do with it anyway! */
        (void)Curl_done(&easy->easy_conn, easy->result, premature);

        if(easy->easy_conn)
          /* the connection is still alive, set back the association to enable
             the check below to trigger TRUE */
          easy->easy_conn->data = easy->easy_handle;
      }
      else
        /* Clear connection pipelines, if Curl_done above was not called */
        Curl_getoff_all_pipelines(easy->easy_handle, easy->easy_conn);
    }

    /* figure out if the easy handle is used by one or more connections in the
       cache */
    multi_connc_remove_handle(multi, easy->easy_handle);

    if(easy->easy_handle->state.connc->type == CONNCACHE_MULTI) {
      /* if this was using the shared connection cache we clear the pointer
         to that since we're not part of that handle anymore */
      easy->easy_handle->state.connc = NULL;

      /* Since we return the connection back to the communal connection pool
         we mark the last connection as inaccessible */
      easy->easy_handle->state.lastconnect = -1;

      /* Modify the connectindex since this handle can't point to the
         connection cache anymore.

         TODO: consider if this is really what we want. The connection cache
         is within the multi handle and that owns the connections so we should
         not need to touch connections like this when we just remove an easy
         handle...
      */
      if(easy->easy_conn && easy_owns_conn &&
         (easy->easy_conn->send_pipe->size +
          easy->easy_conn->recv_pipe->size == 0))
        easy->easy_conn->connectindex = -1;
    }

    /* change state without using multistate(), only to make singlesocket() do
       what we want */
    easy->state = CURLM_STATE_COMPLETED;
    singlesocket(multi, easy); /* to let the application know what sockets
                                  that vanish with this handle */

    Curl_easy_addmulti(easy->easy_handle, NULL); /* clear the association
                                                    to this multi handle */

    {
      /* make sure there's no pending message in the queue sent from this easy
         handle */
      struct curl_llist_element *e;

      for(e = multi->msglist->head; e; e = e->next) {
        struct Curl_message *msg = e->ptr;

        if(msg->extmsg.easy_handle == easy->easy_handle) {
          Curl_llist_remove(multi->msglist, e, NULL);
          /* there can only be one from this specific handle */
          break;
        }
      }
    }

    /* make the previous node point to our next */
    if(easy->prev)
      easy->prev->next = easy->next;
    /* make our next point to our previous node */
    if(easy->next)
      easy->next->prev = easy->prev;

    easy->easy_handle->set.one_easy = NULL; /* detached */

    /* Null the position in the controlling structure */
    easy->easy_handle->multi_pos = NULL;

    /* NOTE NOTE NOTE
       We do not touch the easy handle here! */
    free(easy);

    multi->num_easy--; /* one less to care about now */

    update_timer(multi);
    return CURLM_OK;
  }
  else
    return CURLM_BAD_EASY_HANDLE; /* twasn't found */
}

bool Curl_multi_canPipeline(const struct Curl_multi* multi)
{
  return multi->pipelining_enabled;
}

void Curl_multi_handlePipeBreak(struct SessionHandle *data)
{
  struct Curl_one_easy *one_easy = data->set.one_easy;

  if(one_easy)
    one_easy->easy_conn = NULL;
}

static int waitconnect_getsock(struct connectdata *conn,
                               curl_socket_t *sock,
                               int numsocks)
{
  if(!numsocks)
    return GETSOCK_BLANK;

  sock[0] = conn->sock[FIRSTSOCKET];

  /* when we've sent a CONNECT to a proxy, we should rather wait for the
     socket to become readable to be able to get the response headers */
  if(conn->bits.tunnel_connecting)
    return GETSOCK_READSOCK(0);

  return GETSOCK_WRITESOCK(0);
}

static int domore_getsock(struct connectdata *conn,
                          curl_socket_t *sock,
                          int numsocks)
{
  if(!numsocks)
    return GETSOCK_BLANK;

  /* When in DO_MORE state, we could be either waiting for us
     to connect to a remote site, or we could wait for that site
     to connect to us. It makes a difference in the way: if we
     connect to the site we wait for the socket to become writable, if
     the site connects to us we wait for it to become readable */
  sock[0] = conn->sock[SECONDARYSOCKET];

  return GETSOCK_WRITESOCK(0);
}

/* returns bitmapped flags for this handle and its sockets */
static int multi_getsock(struct Curl_one_easy *easy,
                         curl_socket_t *socks, /* points to numsocks number
                                                  of sockets */
                         int numsocks)
{
  /* If the pipe broke, or if there's no connection left for this easy handle,
     then we MUST bail out now with no bitmask set. The no connection case can
     happen when this is called from curl_multi_remove_handle() =>
     singlesocket() => multi_getsock().
  */
  if(easy->easy_handle->state.pipe_broke || !easy->easy_conn)
    return 0;

  if(easy->state > CURLM_STATE_CONNECT &&
     easy->state < CURLM_STATE_COMPLETED) {
    /* Set up ownership correctly */
    easy->easy_conn->data = easy->easy_handle;
  }

  switch(easy->state) {
  default:
#if 0 /* switch back on these cases to get the compiler to check for all enums
         to be present */
  case CURLM_STATE_TOOFAST:  /* returns 0, so will not select. */
  case CURLM_STATE_COMPLETED:
  case CURLM_STATE_MSGSENT:
  case CURLM_STATE_INIT:
  case CURLM_STATE_CONNECT:
  case CURLM_STATE_WAITDO:
  case CURLM_STATE_DONE:
  case CURLM_STATE_LAST:
    /* this will get called with CURLM_STATE_COMPLETED when a handle is
       removed */
#endif
    return 0;

  case CURLM_STATE_WAITRESOLVE:
    return Curl_resolver_getsock(easy->easy_conn, socks, numsocks);

  case CURLM_STATE_PROTOCONNECT:
    return Curl_protocol_getsock(easy->easy_conn, socks, numsocks);

  case CURLM_STATE_DO:
  case CURLM_STATE_DOING:
    return Curl_doing_getsock(easy->easy_conn, socks, numsocks);

  case CURLM_STATE_WAITPROXYCONNECT:
  case CURLM_STATE_WAITCONNECT:
    return waitconnect_getsock(easy->easy_conn, socks, numsocks);

  case CURLM_STATE_DO_MORE:
    return domore_getsock(easy->easy_conn, socks, numsocks);

  case CURLM_STATE_DO_DONE: /* since is set after DO is completed, we switch
                               to waiting for the same as the *PERFORM
                               states */
  case CURLM_STATE_PERFORM:
  case CURLM_STATE_WAITPERFORM:
    return Curl_single_getsock(easy->easy_conn, socks, numsocks);
  }

}

CURLMcode curl_multi_fdset(CURLM *multi_handle,
                           fd_set *read_fd_set, fd_set *write_fd_set,
                           fd_set *exc_fd_set, int *max_fd)
{
  /* Scan through all the easy handles to get the file descriptors set.
     Some easy handles may not have connected to the remote host yet,
     and then we must make sure that is done. */
  struct Curl_multi *multi=(struct Curl_multi *)multi_handle;
  struct Curl_one_easy *easy;
  int this_max_fd=-1;
  curl_socket_t sockbunch[MAX_SOCKSPEREASYHANDLE];
  int bitmap;
  int i;
  (void)exc_fd_set; /* not used */

  if(!GOOD_MULTI_HANDLE(multi))
    return CURLM_BAD_HANDLE;

  easy=multi->easy.next;
  while(easy != &multi->easy) {
    bitmap = multi_getsock(easy, sockbunch, MAX_SOCKSPEREASYHANDLE);

    for(i=0; i< MAX_SOCKSPEREASYHANDLE; i++) {
      curl_socket_t s = CURL_SOCKET_BAD;

      if(bitmap & GETSOCK_READSOCK(i)) {
        FD_SET(sockbunch[i], read_fd_set);
        s = sockbunch[i];
      }
      if(bitmap & GETSOCK_WRITESOCK(i)) {
        FD_SET(sockbunch[i], write_fd_set);
        s = sockbunch[i];
      }
      if(s == CURL_SOCKET_BAD)
        /* this socket is unused, break out of loop */
        break;
      else {
        if((int)s > this_max_fd)
          this_max_fd = (int)s;
      }
    }

    easy = easy->next; /* check next handle */
  }

  *max_fd = this_max_fd;

  return CURLM_OK;
}

static CURLMcode multi_runsingle(struct Curl_multi *multi,
                                 struct timeval now,
                                 struct Curl_one_easy *easy)
{
  struct Curl_message *msg = NULL;
  bool connected;
  bool async;
  bool protocol_connect = FALSE;
  bool dophase_done;
  bool done = FALSE;
  CURLMcode result = CURLM_OK;
  struct SingleRequest *k;
  struct SessionHandle *data;
  long timeout_ms;

  if(!GOOD_EASY_HANDLE(easy->easy_handle))
    return CURLM_BAD_EASY_HANDLE;

  data = easy->easy_handle;

  do {
    /* this is a single-iteration do-while loop just to allow a
       break to skip to the end of it */
    bool disconnect_conn = FALSE;

    /* Handle the case when the pipe breaks, i.e., the connection
       we're using gets cleaned up and we're left with nothing. */
    if(data->state.pipe_broke) {
      infof(data, "Pipe broke: handle 0x%p, url = %s\n",
            easy, data->state.path);

      if(easy->state < CURLM_STATE_COMPLETED) {
        /* Head back to the CONNECT state */
        multistate(easy, CURLM_STATE_CONNECT);
        result = CURLM_CALL_MULTI_PERFORM;
        easy->result = CURLE_OK;
      }

      data->state.pipe_broke = FALSE;
      easy->easy_conn = NULL;
      break;
    }

    if(easy->easy_conn && easy->state > CURLM_STATE_CONNECT &&
       easy->state < CURLM_STATE_COMPLETED)
      /* Make sure we set the connection's current owner */
      easy->easy_conn->data = data;

    if(easy->easy_conn &&
       (easy->state >= CURLM_STATE_CONNECT) &&
       (easy->state < CURLM_STATE_COMPLETED)) {
      /* we need to wait for the connect state as only then is the start time
         stored, but we must not check already completed handles */

      timeout_ms = Curl_timeleft(data, &now,
                                 (easy->state <= CURLM_STATE_WAITDO)?
                                 TRUE:FALSE);

      if(timeout_ms < 0) {
        /* Handle timed out */
        if(easy->state == CURLM_STATE_WAITRESOLVE)
          failf(data, "Resolving timed out after %ld milliseconds",
                Curl_tvdiff(now, data->progress.t_startsingle));
        else if(easy->state == CURLM_STATE_WAITCONNECT)
          failf(data, "Connection timed out after %ld milliseconds",
                Curl_tvdiff(now, data->progress.t_startsingle));